As a switching element (a power semiconductor device) performing a high-current switching operation, a power MOSFET, an insulated gate bipolar transistor (IGBT), or the like is used. In a semiconductor device using this switching element, if an overcurrent flows due to a cause such as short-circuiting of a load, or an excessive temperature rise occurs, the switching element may be broken down. Accordingly, in a case where a current flowing in the switching element exceeds a predetermined value, it is effective to make the semiconductor device perform an operation of forcibly interrupting the switching element (an overcurrent protection operation). Also, in a case where the switching element has overheated and the temperature of the switching element exceeds a predetermined value, it is effective to make the semiconductor device perform an operation of forcibly interrupting the switching element (an overheat protection operation).
In this case, the temperature can be measured by attaching a temperature detecting device such as a thermocouple to a semiconductor chip. However, in a case of using a temperature detecting device separate from the semiconductor chip, it is difficult to accurately measure the temperature of the semiconductor chip without a delay. For this reason, it is effective to form a temperature detecting device together with the switching element (such as a power MOSFET or an IGBT) in the semiconductor chip (a semiconductor wafer). In this case, in order to suppress the chip area from increasing, a portion of the switching element (a power MOSFET) may be used for temperature detection. This technology is disclosed in JP-A-2011-142700, for example. In this technology, immediately after the power MOSFET is switched from an OFF state to an ON state, a reverse current flowing in a p-n junction (a parasitic diode) formed in the structure of the power MOSFET is examined.
In the technology disclosed in JP-A-2011-142700, a reverse recovery time (or a reverse recovery current) of the parasitic diode is measured, whereby the temperature is estimated. The measured temperature is the temperature of the p-n junction constituting a portion of the switching element (the power MOSFET). Therefore, it is possible to more accurately measure the temperature without a delay as compared to a case of using a temperature detecting device. Also, it is unnecessary to separately form a structure for temperature detection in the semiconductor chip.
In an intelligent power module (IPM), a switching element chip containing a switching element, and a control circuit chip containing a control circuit for performing the above described control (an overcurrent protection operation and an overheat protection operation) are sealed inside the same package. Therefore, it is possible to safely use the switching element.